Electrolysis of acrylamides



United States Patent 3,193,483 ELECTROLYSIS F ACRYLAMIDES Manuel M. Baizer, St. Louis, Mo., assignor to Monsanto Company, a corporation of Delaware No Drawing. Filed Jan. 14, 1964, Ser. No. 337,546 26 Claims. (Cl. 204-73) This application is a continuation-in-part of my copending aplication Serial No. 75,130 filed December 12, 1960, and now forfeited; my copending application Serial No. 145,480, filed'October 16, 1961 and now abandoned: my copending application Serial No. 189,072 filed April 20, 1962; and my copending application Serial No. 234,834 filed November 1, 1962, and now abandoned.

This invention relates to the manufacture'of polyfunctional compounds and more particularly provides a new and valuable electrolytic process for the hydrodimerization of alpha,beta-mono-olefinic carboxamides.

The present invention is concerned with the hydro-' dimerization, i.e., the reductive dimerization, of certain olefinic compounds to obtain saturated dimers thereof.

A general object of the invention is the provision of an improved process for the preparation of alkane dior tetra-carboxamides. A further object is the provision of a technically feasible, electrolytic process for the conversion of alpha,beta-mono-olefinic monoor di-carboxamides to parafiinic dior tetra-carboxamides. Another object is the provision of a technically feasible, electrolytic process for the conversion of aliphatic, alpha, beta-olefinic carboxamides to paraifinic carboxamides. Still another object is the electrolytic conversion of aliphatic alpha,beta-olefinic dicar-boxamides to parafiinic tetra-carboxamides. An important object of the invention is the provision of an electrolytic process of converting alpha,beta-mono-olefinc carboxamides to obtain good yields of the saturated dimers thereof rather than a preponderance of hydrogenated monomers and/or complex organometallic compounds. A very important objective of the invent-ion is the provision of an electrolytic process wherein there are obtained better than 50% and even better than 80% up to substantially theoretical yields of hydrodimer-ization products of the alpha,beta-monoolefinic carboxamides employed in the process.

These and other objects of the invention hereinafter described are provided by the present process for conducting the hydrodimerization of an olefinic carboxamide of, for example, from 3 to 8 carbon atoms. which comprises subjecting to electrolysis, in contact with a cathode, a solution of the olefinic carboxamide in an aqueous electrolyte under non-polymerizing conditions such that the desired hydrodimer is obtained and recovered in good yield. It is desirable to employ fairly concentrated solut-ions in order to minimize undesired reactions of intermediate ions with the water of the electrolyte. Ordinarily the average amount of the amide reactants will be at least about by weight of the catholyte, and preferably at least 10% by weight or more. The process is usually characterized by fairly high concentrations of salts .in the catholyte, generally constituting at least 5% by weight of the catholyte and usually constituting 30% or more by weight of the total amount of salt and water in the catholyte, in order to obtain the desired solubility of the olefinic carboxamide and the desired conductivity.

The salt concentration has an important bearing upon the results obtained. When the salts are hydrotropic, high concentrations contribute to solubility of the al- 3,193,483 Patented July s, 1965 pha,beta-olefinic carboxamides, making it possible to utilize higher concentrations of the carboxamides. But beyond this, the concentration of salt cat-ions'in some way affects the course of the reaction and resultssin higher yields of hydrodimers at the expense of products, simple reduction products. The process of the present invention is carried out utilizing a supporting electrolyte as understood by those in the art, i.e., electrolyte capable of carrying current but not discharging under the electrolysis conditions, but with the requirement that the supporting electrolyte be a salt and that it constitute at least 5% by weight of the solution electrolyzed. The requirements of supporting electrolytes are well understood by those skilled in the art and they will be able to select such electrolytes and utilize them in the proper concentrations in view of the teaching herein as to catholyte required for hydrodime rizations of alpha,beta-olefinic carboxamides, and salt concentrations essential .to such hydrodimerizations. As the hydrodimerization of N,N-diethylcarboxamides, for example, proceeds at the cathode voltages which can vary from, say, about 1.9 to about -2.15 volts, (vs. saturated calomel electrode), depending somewhat upon conditions. any electrolyte salts not subject to substantial discharge at less negative conditions can be employed, and to some extent those discharging at about 1.8 to 1.9 volts (vs. saturated calomel electrode). Thus. extensive classes of suitable electrolyte salts are available for use. The salts can be organic or inorganic. or mixtures of such, and composed of simple cations and anions or very large complex cations and anions. The term salts is employed herein in its generally recognized sense to indicate a compound composed of a cation and an anion, such as produced by reaction of an acid with a base.

It is preferred that the salts employed here-in have the properties of that class of salts recognized as hydrotropic, i.e., as promoting the solubility of organic compounds in water. fates, etc., have hydrotropic effects. In this application, any salt which increases the solubility of olefinic carboxamides in water is considered hydrotropic.

Some olefinic compounds are subject to polymerization Or other side reactions if the electrolyte is acidic, or excessively alkaline, and it will be desirable in such cases to conduct the reductive coupling in solutions which are not overly acidic and also in some cases below a pH at which undesirable side reactions occur, e.g., below about 12. To minimize polymerization, simple reduction of the olefinic bond and other side reactions, the pH is usually maintained in the range of about 3 to about 12, preferably 6 to 9.5. In addition, when the catholyte during electrolysis is acidic, it will generally be advisable to conduct the electrolysis under conditions which inhibit polymerization of the reactants involved or in the presence of a polymerization inhibitor, for example, in an atmosphere containing sufiicient oxygen to inhibit the polymerization in question, or in the presence of inhibitors effective for inhibiting free radical polymerization. Classes of inhibitors for inhibiting free radical polymerizations are well known, e.g., such inhibitors as hydroquinone, p-t-butyl catechol, quinone, p-nitrosodimethylaniline, di-t-butyl hydroquinone, 2,5-dihydroxy-1,4-benzoquinone, 1,4-naphthoquinone, chloranil, 9,l0-phenanthraquinone, 4-aminol-naphthol, etc., are suitable. The present process will ordinarily be conducted in the absence of free radical polymerization catalysts or materials which will form Various organic sulfonates, alkyl sulpolymerization catalysts un although their presence is not necessarily undesirable if der the electrolysis conditions,

polymerization is sutliciently inhibited or conditions are otherwise such that polymerization will not occur. The inhibitors are ordinarily used in small amounts, e.g., less than 1% by weight based on the olefinic carboxamidc, for

. example 0.01% by weight based on the olefinic carboxamide, but can be used in larger amounts such as up to 5% or more by weight, based on the olefinic carboxarnide.

Even though suitable inhibitors are employed, the yields are generally markedly better under conditions which are'not greatly acidic. However, the deleterious effects of acidity can be to some extent overcome by use of fairly high current densities, such as over amperes/ dm. of cathode surface, and a rapidly circulating electrolyte systemythis may be due to the supply of electrons on the cathode surface making such surface alkaline despite acidity in the bulk of the solution. In addition high salt concentrations mitigate the effect of acidity by carrying a large share of the current, particularly at high current densities. Even under acidic conditions, the concentration of the salt cation which does not discharge under the electrolysis conditions is markedly greater than that of the hydrogen ion. For example even at a pH of 2, the hydrogen ion concentration is only 0.01 N, which is many times less than the usual salt cation concentration. In fact, the concentration (normality) of the salt cation will generally be at least 10 times that the hydrogen ion and often 100 times that of the hydrogen ion. The effect of small amounts of cations which discharge at less negative potentials can similarly be masked by high concentrations of more suitable cations. For example, in the case of N,N-diethylcrotonarnide sodium or potassium salts can definitely be used as supporting electrolyte, but their use results in lower yields as will be discussed in more detail hereinbelow, and for this reason it is definitely preferred to utilize salt cations of more negative discharge potentials than sodium. However, small amounts of sodium or potassium salts, such as 2 or 3% by weight of the total catholyte containing more suitable salts do not have any pronounced etfech'although large amounts tend to cause a marked lowering of yield of the desired hydrodimer. It is desirable that the salt employed have a high degree of water solubility to permit use of very concentrated solutions; for concentrated salt solutions dissolve greater amounts of the olefinic carboxamide; specifically when the salts employed have a hydrotropic effect. It is generally desirable that the salt constitute more than by weight of the total amount of salt and water in solution, and much greater amounts .can, of course be employed. However, lower concentrations can be used, particularly if polar solvents are used alongwith the water and salt, although it ispreferred on a cost basis to avoid the use of polar solvents. It will be recognized that the pH considerations with respect to the catholyte solution make it desirable to avoid any concentration of highly basic or acidic salts.

In addition to the foregoing considerations, a number of other factors are important in selecting salts suitable for good results. For example, it is undesirable that the salt cation form an insoluble hydroxide at the operating pH, or that it discharge on-the cathode forming an alloy which substantially changes the hydrogen overvoltage and leads to poorer current. efficiencies. The salt anion should not be lost by discharge at the anode with possible formation of by-products. In a cell containing a separating membrane is used, it is desirable to avoid types of anions which, in contact with hydrogen ions present in the anolyte chamber would form insoluble acids and clog the pores of the membrane.

In general amine and quaternary ammonium salts are suitable for use in the present process. Alkali and alkaline earth metal salts can also be used, althoughthe alkali metals are somewhat more subject to interfering discharge,

water solubility.

' N,. I-dibut yl-Z-pentenantidc While the molecular size of the olefinic compounds to be dimeriz'ed is not controlling, -in general'olefinic compounds containing more than 20 carbon atoms will be of little or no interest. It is generally preferable that the amide group be the only'functional group other than the olefinic bond, i.e., that the compound be hydrocarbon containing no non-benzenoid unsaturation, except for the olefin and amide groups, which, of course, contain nitrogen and oxygen, as well as a non-benzenoid double bond. It will be recognized that there are many possible variations of such suitable carboxamides; for example, acrylamides, N,N-dialkylacrylamides,' crotonamides, N,N-dialkylcrotonamides, methacrylamides, N,N-dialkylmethacrylamides and various other alk-l-enyl carboxamides as well as beta-phenylacrylamide and various other amides of cinnamie acid ,can be suitably hydrodimerized by the presently claimed procedure. Particularly suitable alkl-cnyl carboxamides are represented by the formula:

in which R'is an alkenyl radical unsaturated in the-1,2- positionand R is hydrogen or alkyl.

Hydrodimerization by the present process of various alpha,bet a-olefinic monoor 'carboxamides is shown in the table below, wherein the alpha,beta-olefinic monomeric compound and the saturated dimer obtained therefrom are given. The hyd'rodimerization product is that to be expected from head-to-head addition, i.e., coupling at the carbon atom betavto thefunctional group, e.g., N,N- dibutylmethacrylamide is converted by the present process to N,N,N,N-tetrabutyl-2,S-dimethyladipamide.

Alpha, Beta-olefinic Amide Hydrodimerization Product N,N-dictliylcrotonamide N,N,NN-tet.raethyl 3,4-

' dimethylarlipamide.

- iliethyladipamide. N,N-tlimethyl-2-methylenc- N N ,N ',N -tetrnmethyl-2,5-

valcramide. dipropylndipnmide. N,N-tlipontyl-2,3-(llethyl- N,N,N ,N-tet.rapentyl 3,4-

crotouumitlc. dimeth yl-Z,3,4,5-tetraet hyladipamide.

- 4,5.6,7-tetruearboxamide. A orylamideus Adipaimde. Methaeryluuiide Dimethyladipnmide. N-butytmethacrylamide N ,N-dibutyl-2,5-dimethyladipa- N,Nwgethykbeta-phenylacryl- N,N,N,N-tetrnethyl moluamide..-

nude. N,N,N,N-tetrncthyl beta, B1111 beta-dlphenyladipamide.

When working with some of the substituted acrylamides there is often obtained a mixture of stereo-isomeric hydrogenated dimers. Thus, from methacrylamide there is obtained. a mixture of the dl and meso-2,5-di-methyladipamides. For most industrial uses, however, e.g., for preparation of condensation polymers, both isomers are useful; so that generally no occasion arises for requiring separation of the two isomers. However, if desired, this may be etfected by methods known to those skilled in the art, e.g., close fractional distillation, crystallization, etc.

In carrying out the process of this invention, a solution for electrolysis is prepared by adding the olefinic carboxamide to an aqueous solution (preferably about "30% or more by weight) of the conducting salt to give a solution which contains at least 5% by weight, based on the total weight of the solution, of the olefinic carboxamide in the dissolved state. Depending upon the quantity of salt present and the nature thereof, there may thus be obtained true solutions containing as much as 50% or more by weight of the olefinic carboxamide. The concentration of olefinic carboxamide in the dissolved state is to some extent a function of salt concentration; however, at temperatures of above room temperature, i.e., at above, say, 35 C., less of the salt is required to obtain optimum concentration of dissolved olefinic carboxamide than is required at room temperature. Because the extent of hydrodimerization appears to be related to the concentration of theolefinic carboxamide in the electrolysis solution, when the electrolysis is to be conducted at room temperature, the olefinic carboxamide is ad vantageously added to a saturated aqueous solution of the salt in order to obtain thereby as high a concentration as possible of the dissolved olefini'c carboxamide. When the electrolysis is to he conducted at a temperature of above room temperature, high concentrations of olefinic carboxamide can be attained with unsaturated solutions of the salt, i.e., the salt may be as low as 30% by weight of the electrolysis solution. Concentration of the olefinic carboxamide in the electrolysis solution may also be increased by using a mixture of water and a polar solvent, e'.g;, acetonitrile, dioxane, ethylene glycol, dimethylformamide, dimethylacetamide, ethanol or isopropanol, together with the aromatic salt.

An electrolytic cell preferably having a cathode of high hydrogen overvoltage is charged with the thus prepared solution and an electric current is passed through the cell to eflFect the hydrodimerization reaction. Depending upon the concentration of the olefinic carboxamide and upon the hydrogen ion concentration of the solution, there may or may not be'formed products other than the saturated dimer. Thus, when working with concentrations of olefinic carboxamide which are less than or from 10 to by weight of the solution, there may be formed, in addition to the hydrodimerization product, compounds such as the reduced monomers or other condenastion products. With acrylamide, for example, propionamide may thus be obtained as a byproduct. The-hydrogen ion concentration of the solution will ordinarily be such as to give a pH of 7 or higher, as neutral or mildly alkaline solutions are ordinarily preferred. Many of the olefinic carboxamides tend to polymerize when electrolyzed in strongly acidic solution, such as solutions of mineral acids, and it is desirable in such cases to avoid excessive acidity, making it desirable to operate at pHs above about 5 or 6. such as pro vided by solutions of salts of strong'bases. Moreover. the hydrogen ion has a cathode discharge potential of about l.5 volts, making it desirable to avoid high concentrations of hydrogen ion in the. catholyte if the hydrodimerization occurs at similar orfmore negative cathode potentials. The hydrodimerization can suitably be conducted at pHs higher than those a which substantial polymerization of olefinic compoun occurs, or higher than pH's at which there is undue generation of hydrogen, for example, at pHs higher than;those at which more than half the current is expended in discharging hydrogen ions. The pI-Is referred to are those obtaining in the bulk of the catholyte solution, such as determinable by 'a pH meter on a sample of the catholyte removed from the cell. The electrolysis in effect generates acid at the anode and base at the cathode; it will be recognized that in an undivided cell the pH in the immediate vicinity of the cathode may differ considerably from that near the anode, particularly if good stirring is not employed. To some extent the effects of acidity can be counteracted by high current den sity to cause more rapid generation of hydroxyl ions. However, high current densities also require good stirring or turbulence to move the reactants to the cathode.

During electrolysis in a divided cell, alkalinity increases in the catholyte. However, the anolyte becomes acidic. When a porous diaphragm is used to separate the catholyte from the anolyte, the alkalinity of the catholyte will depend upon the rate of diffusion of acid from the anolyte through the porous barrier. Control of alkalinity in the catholyte, when employing a diaphragm, may thus be realized by purposely leaking acid from the anolyte into the catholyte. It can also be achieved, of course, by extraneous addition to the catholyte of an acid material, e.g., glacial acetic acid, phosphoric acid or p-toluenesulfonic acid. Alkalinity may also be controlled, whether or not a diaphragm is used in the cell, by employing bufier systems of cations which will maintain the pH range while not reacting at the reaction conditions. Control of alkalinity becomes particularly necessary if the electrolytic hydrodimerization is carried to a high conversion, or if it is conducted in a continuous manner with continuous or intermittent addition of carboxamide-and removal of product. while the electrolyte itself stays in the cell or is recycled to the cell. While a successful hydrodimerization could be successfully conducted for some period of time without provisions to counteract the alkalinity, it is apparent that eventualIy the build-up of hydroxyl ions in the catholyte of a divided cell would be such as to cause undesirable side-reactionsto predominate. Therefore, for high conversion or continuous procedures it is necessary to employ a means for controlling the alkalinity. In general it is undesirable that the alkalinity rise so high as to tend to cause substantial hydrolysis of the carboxamide reactant and it will be desirable to maintain the pH at values no greater than 9.5 or 10, although higher pHs can be employed. Good agitation or turbulence counteracts excess alkalinity to some extent, by minimizing local concentrations of hydroxyl ions at the cathode, making it possible to operate efficiently at higher bulk pHs. Moreover, good agitation maintains a suitable carboxamide concentration near the cathode and keeps the electrolysis rate and use of high current densities from being unnecessarily limited by slow diffusion rates. Agitation as used herein is intended to include movement of the electrolysis medium whether resulting from stirring, beating, vibration, pumping or bubbling fluids through the medium, circulation of the medium itself. with or without baffiing, and various other means of causing currents in the electrolyte medium or admixture of the components thereof.

The term consisting essentially of as employed herein with respect to the solutions electrolyzed is intended to leave the solutions open to addition of other components which do not change the basic nature of the solutions with respect to the electrolytic hydrodimerization process being conducted therein. I

When a divided cell is employed, it will often be desirable to use an acid as the anolyte, any acid being suitable, particularly dilute mineral acids such as sulfuric or phosphoric acid. Hydrochloric acid can be employed but would have the disadvantage of generating chlorine at the anode, and of being more corrosive with respect to some anode materials. If desired. a salt solution can be used as anolyte, those useful as catholyte also being suitable as anolyte. although there are many other salt solu-' tions suitable for such use. It will be recognized that the descriptions of the catholyte or carboxamide solutions herein apply to the solutions, regardless of whether they are in an undivided cell serving as both catholyte and anolyte. or are in the cathode-containing portion of a divided cell. Conversely, when a divided cell is employed, the various descriptions of the catholyte do not necessarily apply to the anolyte, as the olefinic carboxamide is not ordinarily present in the anolyte and the character of the anolyte is not of primary importance to the hydrodimerization reaction which is occurring in the catholyte. As a practical matter, to obtain good yields in the operation of a continuous process over a matter of days or weeks, it, may be necessary to employ a divided cell to avoid or minimize interfering reactions, such as resulting from generation of hydrogen ions at the anode or resulting in deposition of various salt materials on the anode. Moreover, many suitable catholyte salts are subject to degradation if permitted to contact the anode, making it advantageous to employ mineral acids as the anolyte in a divided cell.

In the past various electrolysis reactions for reducing or otherwise altering organic compounds have been known. In general, however, such reactions have had the disadvantage of being of small scale and low velocity decimeter and higher, even up to 100 or more amperes/ square decimeter, and it is further possible to use cells having a large effective electrode area, whether in a single set ofelectrodes or in a series of electrodes. Thus in commercial practice it is probable that individual cells will draw at least 20 to 30 amperes, most likely more than 100 ampcres,.and cells drawing more than 1000 amperes are contemplated. 'For reasons of economics and to make practical use of such current densities without necessitating prohibitively high cell voltages, it is essential to have fairly low resistance in the cell as obtainable by utilizing fairly high concentrations of the electrolyte salt and a relatively narrow gap between the electrodes, e.g., no more than one-half inch. and preferably of the order of one-fourth inch or smaller. Applied voltages of to 20 volts for current densities of 15 to 40 amperes/dm. are suitable. and it is preferable, in this range as well as at higher densities that the applied voltage have a numerical value no greater than one-half the numerical value of the current density (in amperes/dmfi). Various ,power sources are suitable for use in the present invention,- particularly any efiicient sources of direct current, and, if desired. various known means of varying the applied potential to regulate the current densityand the'cathode potential can be employed, for example the means described in Metcalf et al., US. Patent No. 2,835,631 issued May 20, 1958, the disclosure of which is incorporated herein by reference. If desired alternating current can be superimposed on the direct current applied to the cell.

Materials suitable for constructing the electrolysis cell employed in the present processare well known to those skilled in the art. The electrodes can be of any'suitable cathode'and anode material. The anode may be of virtually any conductor. although it will usually be advantageous to employ those that are relatively inert or attacked or corroded only slowly by the electrolytes; suitable anodes are, for example, platinum, carbon, gold, nickel, nickel silicide, Duriron, lead, and lead-antimony and lead-copper alloys. and alloys of various of the foregoing and other metals.

Anysuitable material can be employed as cathode, various metals and alloys being known to the art. it is gen erally advantageous to employ metals of fairly high hydrogen overvoltage in order to promote current efiiciency and minimize generation of hydrogen'during electrolysis. In general it will be desirable to employcathodcs having overvoltages at least about as great as that of copper. as determined in a 2N sulfuric acid solution at current density of 1 milliamp/squarecentimeter (Carman. Chemical Constitution and Properties of Engineering Materials, Edward Arnold and Co., London. l949, page 290). Suitable electrode materials include, for example. mercury, cadmium, tin, zinc, bismuth. lead, graphite. aluminum, nickel, etc., in general those of higher over-voltage being preferred, although those of lower hydrogen overvoltage can also be employed, even if they cause generation of hydrogen under the electrolysis conditions,-as is the case with stainless steel and other electrodes of lower hydrogen overvoltage. It will be realized that overvoltage can vary with the type of surface and prior history of. the metal as well as with other factors; therefore the term overvoltage as used herein with respect to copper as a gauge has reference to the overvoltage under the conditions of use in electrolysis.

Among the salts which can be employed according to the invention for obtaining the desired concentration of dissolved olefinic carboxamide, the amine and quaternary ammonium salts are generally suitable, especially those of sull'onic and alkyl sulfuric acids. Such salts can he the saturated aliphatic amine salts or heterocyclic amine salts,

e.g., the mono-, rlior trialkylamine salts, or the mono-, dior trialkanolaminc salts, or the piperidine, pyrrolidine or morpholine salts, e.g., the ethylamine. dimethylamine or triisopropylamine salts of various acids, especially various sulfonic acids. Especially preferred are aliphatic and heterocyclic quaternary ammonium salts, i.e., the tetraalkylammonium or the tetraalkanolammonium salts or mixed alkyl alkanol ammonium salts such as the alkyltrialkanolammonium, the dialkyldialkanolammonium, the alkanoltrialkylammoniurn or the N-heterocyclic N-alkyl ammonium salts of sulfonic or other suitable acids. The saturated aliphatic or heterocyclic quaternary ammonium cations in general have suitably high cathode discharge potentials for use in the present invention and readily form salts having suitably high water solubility with anions suitable for use in the electrolytes employed in the present invention. The saturated, aliphatic or heterocyclic quaternary ammonium salts are therefore in general well adapted to dissolving high amounts of olefinic carboxamides in their aqueous solutions and to effecting reductive couplings of such olefinic compounds. It is understood, of course, that it is undesirable that the ammonium groups contain any reactive groups which might interfere to some extent with the reductive coupling reaction. In this connection it should be noted that aromatic unsaturation as such does not interfere as benzyl substituted ammonium .p-toluenesulfonic acid, o-, mor p-ethylbenzenesulfonic acid, o-', mor p-cumenesulfonic acid, o-, mor p-tertamylbenzenesulfonic acid; o-, mor p-hexylbenzenesulfonic acid. o-xylene-4-sulfonic acid, p-xylene-Z-sulfonic acid, m-xylene-4 or 5-sulfonic acid, mesitylene-Z-sulfonic acid, durene-3-sulfonic acid, pentamethylbenzenesulfonic acid. o-dipropylbenzene-4-sulfonic acid, alphaor betanaphthalenesulfonic acid, o-, mor p-biphenylsulfonic acid, and alpha-methyl-beta-naphthalenesulfonic acid. Alkal metal salts are useful in the present invention with certain limitations, and the alkali metal salts of such sulfonic acids can be employed, i.e., the sodium, potassium, lithium, cesium or rubidium-salts such as sodium benzenesulfonate, potassium p-toluenesulfonate, lithiuin o-biphenylsulfonate, rubidium beta-naphthalenesulfonate, cesium p-ethylbenzenesulfonate, sodium o-xylene-3-sulfonate. or potassium pentamethylbenzenesulfonate. The salts of such sulfonic acids may also be the saturated, aliphatic amine or heterocyclic amine salts, e.g., the mono-, dior trialkylamine salts. or the monodi or trialkanolamine salts, or the piperidine. pyrrolidine, or morpholine salts, e.g., the ethylamine, dimethylamine or triisopropylamine salt of benzenesulfonic acid or of o-, por m-toluenesulfonic acid: the isopropanolamine, dibutanolamine or triethanolamine salt of o-. por m-toluenesulfonic acid or of o-, por m-biphenylsulfonic acid, the piperidine salt of alphaor beta-naphthalenesulfonic acid or of the cumenesulfonic acids: the pyrrolidine salt of o-, mor p-amylbenzenesulfonate; the morpholine salt of benzenesulfonic acid, of o-, mor p-toluenesulfonic acid, or of alphaor beta naphthalenesulfo'nic acid etc. In general, the sulfonates of any of the ammonium cations disclosed generically or specifically herein can be employed in the present invention. The aliphatic sulfonates are prepared by reaction of the correspondingly substituted ammonium hydroxide with the sulfonic acid or with an acyl halide thereof. For example. by reaction of a sulfonic acid such as ptoluenesulfonic acid with a tetraalkylammonium hydroxide such as tetraethylammonium hydroxide there is obtained tctraethylammonium p-toluenesulfonate, use of which in the presently provided process has been found to give very good results. Other presently useful quaternary ammonium sulfonates are, e.g., tetracthylammonium or mtoluenesulfonate or benzenesulfonate; tetraethylammonium 0-, mor p-cumenesulfonate, or o-, mor p-ethylbenzenesulfonate, tetramethylammonium benzenesulfonate, or o-, mor p-toluenesulfonate: N,N-di-methyl-piperidinium o-, mor p-toluenesulfonate or 0-, mor pbiphenylsulfonate; tetrabutylammonium alphaor betanaphthalenesulfonate or o-, mor p-toluenesulfonate; tetrapropylammonium o-, mor p-amylbenzenesulfonate or alpha-ethyl-beta-naphthalenc sulfonate;

sulfonate; tctrabutanolammoniuni benzenesulfonate or p- Xylene-3-sulfonate; tctrapentylammonium o, mor ptoluenesulfonate or o-, mor p-hexylbenzenesulfonate, tetrapentanolammonium p-cymene-3-sulfonate or benzene sulfonate, methyl triethylammonium o-, m-, or p-toluene sulfonate or mesitylene-2-sulfonate; trimethyletbylammonium o-xylene-4-sulfonate or o-, mor p-toluenesulfonate; triethylpentylammonium alphaor beta-naphthalenesulfonate or o-, mor p-butylbenzenesulfonate, trimethylethanolammonium benzenesulfonate or o-, mor p-toluenesulfonate: N,N-di-ethylpiperidinum or N-methyl-pyrrolidinum, omor p-hexylbenzenesulfonate or o-, mor p-toluenesulfonate, N,N-di-isopropyl or N,N-di-buty1morpholiniu'm, o-, mor p-toluenesulfonate or o-, mor pbiph'enylsulfonate etc.

The tetraalkylammonium salts of the aryl or alkarylsulfonic acids are generally preferred for use as the salt constituents of the electrolysis solution because the electrolyses in the tetraalkylammonium sulfonates are exclusively electrochemical processes. Employing the same concentration of alpha,beta-olefinic compound, the same cathodic voltage, but using the alkali metal sulfonates instead of the tetraalkylammonium sulfonates, yields of hydrodimerization products are lower than those obtained with the tetraalkylammonium sulofnates. This is true even when there is present in the catholyte the high concentration of olefinic compound which can be attained by employing with the alkali metal sulfonate a co-solvent such as dimethylformamide. This is probably because at cathode voltages at which the hydrodimerization' takes place, the alkali metal salts are also affected. Particularly when solutions containing the alkali metal sulfonates are stirred, the cathodic voltage necessary for hydrodimerization results also in discharging some alkali metal ions. Owing to the presence of these resulting metals, a chemical path is taken which results also in formation of the saturated monomer rather than the hydrodimerization product. In the case of acrylamide, for example, propionamide is also obtained as byproduct. This probably occurs by 1,4- or 1,2- addition of the alkali metal ion to the acrylamide and decomposition by water of the resulting addition product to give the propionamide. Whereas, according to the presently provided process. the two-competing reactions, i.e.. the formation of hydrodimerization products versus formation of saturated monomer, can be manipulated to favor the hydrodimerization, nevertheless, some saturated monomer is formed when the electrolysis solution contains the alkali metal sulfonates rather than the tetraalkylammonium sulfonates, and the yield of hydrodimer is thereby decreased. On the other hand, purely chemical reaction'does not take place when the tetraalkylammonium sulfonatcs are used instead of the alkali metal sulfonates. This is because at cathodic voltages which favor the hydrodimerization reaction, the tetraalkylammonium ion is not discharged. In the case of N,N-diethylcrotonamide. for example, the optimum cathode voltage for conversion to the hydrodimerization product can vary from. say about l.9 volts to about 2.l5 volts. as determined in a stirred run (versus the saturated calomel electrode). There is no lowering in yield of hydrodimerization product by chemical mediation such as that which occurs by use of the alkali metal sulfonatcs. for the tctraalkylammonium ion is not discharged at the operating voltage. For example, when a solution of N,N-diethylcrot0namide in aqueous tctraethanolam-. moium o-, mor p-cumenesulfonate or o-, mor p-tolueneniums aryl or alkaryl sulfonates herein disclosed are of I tetraethylammonium p-tolucnesulfonate is submitted to electrolysis, hydrodimerization occurs at about 1.95 volts, whereas the tetraethylammonium ion is not dis-' charged until about -25 cathodic volts. On the other hand, some olefinic amides are 'hydrodimerized at somewhat less negative cathodic voltages, permitting successful results to be obtained with salts of alkali metals. However, in order to insure against interfering reactions it is usually preferred to employ 'salts of cations which have more strongly negative discharge potentials, e.g., more negative than -2.2 cathodic volts versus the saturated calomel electrode.

Among the ammonium and amine sulfonates useful as electrolytes in the present invention are the alkyl, aralkyl, and heterocyclic amine and ammonium sulfonates, in which ordinarily the individual substitutentson the nitrogen atom contain no more than 10 atoms, and usually the amine or ammonium radical contains from 3 to 20 carbon atoms. It will be understood, of course, that diand poly amines and diand poly ammonium radicals are operable and included by the terms amine and ammo-.

nium. The sulfonate radical can be from aryl, alkyl, alkaryl or aralkyl sulfonic acids of various molecular weights up to for example 20 carbon atoms, and can include one. two or more sulfonate groups. Any of the quaternary ammonium sulfonates disclosed and claimed in my copending application Serial No. 75,123 filed December 12, 1960 can suitably be employed.

Tetraethylammonium p-toluenesulfonate is particularly valuable as the salt constituent of the electrolysis solution in the presently provided hydrodimerization process. However, I have also found that the tetraethylammonium p-toluenesulfonate as well as the other tetraalkylammogeneral utility in electrolytic reduction processes. The

present invention thus provides generally an electrolytic reduction process comprising submitting to electrolysis an aqueous solution of a reducible compound and a tetra alkylammonium salt of a sulfonic acid selected from the class consisting of aromatic aliphatic and aliphaticaromatic sulfonic acids having from 1 to 6 carbon atoms in each alkyl radical and from 6 to 12 carbon atoms in the acid portion of the molecule.

Another especially suitable class of salts for use in the" present invention are the alkylsulfate salts such as methosulfate salts, particularly the amine and quaternary ammonium methosulfate salts. Methosulfate salts such as the methyltriethylammonium, tri-n-propylmethylammonium, triamylmethylammonium, tri-n-butylmethylammonium, etc. are very hygroscopic and the tri-n-butyl-methylammonium in particular forms very concentrated aqueous solutions which dissolve large amounts of organic materials. In general the amine and ammonium cations suitable for use in the alkylsulfate salts are the same as those for the sulfonates.

Aside from their advantageous properties. suitable methosulfates are readily prepared by reacting ethanolio solutions of dimethylsulfate with trialkyl amines, thereby producing methyltrialkylammonium methosulfates.

Various other cations are suitable for use in the present invention, e.g., tetraalkylphosphonium and trialkyl sulfonium cations, particularly as sulfonate salts formed from sulfonic acids as described above, or as methosulfate salts.

As a further illustration of electrolytes suitable for use in the present invention, the following named salts have all successfully been employed in hydrodimerizations to obtain hydrodimers as the major product with little or no formation of impurities, generally employing concentrated aqueous solutions of the salts containing at least 15% and usually 20 to 40% by weight olefin, and utilizing the general procedures of the illustrative examples herein:

(1) N-trimethyl-N-trimethylethylenediammon-ium di-ptolucnesulfonate Various other quaternary ammonium, tetraalkylphosphonium or trialkylsulfonium salts can be employed, in the process in general as well as in the hydrodimerization of N,N-diethylcrotonamid e in particular, e.g., the halides, sulfates, phosphates, phosphonates, acetates and other carboxylic acid salts, benzoates, phosphonates, etc., specifically, for example, tetramethylammonium bromide, tetraethylammonium bromide, tetramethylammonium chloride, tetraallcyl phosphonium chloride,-tetraethylammonium phosphate, etc.; and similarly the alkali, alkaline earth and othermetal salts withthe foregoing anions can be employed, e.g., sodium chloride, potassium phosphates, sodium acetate, calcium acetate, lithium benzoate, calcium chloride, rubidium bromide, magnesium chloride,

as well as the sulfonic acid, particularly aromatic sulfonic acid, and alkylsulfuric acid salts of the foregoing cations and of other alkali, alkaline earth, rare earth and other metals, e.g., cesium, cerium, lanthanum, yttrium, particularly with anions to achieve, sutficient water solubility. The aluminum cation is only somewhat inferior to sodium in respect to its discharge potential, but most salts of aluminum tend to hydrolyze in water and precipitate aluminum oxide. It is understood that the solutions designated herein as containing salts, electrolytes, etc.: in

specified amounts have reference to solutions containing salts sufiiciently stable to remain in solution. It will be recognized that many cations are capable of existing in several valence states, and some valence sta'tes'will be more suitable as supporting electrolytes than others. Other examples of salts which can be employed in the present process, although not necessarily with equivalent or optimum results, are barium bromide, barium acetate, barium propionate, barium adipate, cerium sulfate, cesium chloride, cesium benzoate, cesium benzenesulfonate, potassium oxalate, potassium sulfate, potassium ethyl sulfate, lanthanum acetate, lanthanum benzene sulfonate. sodium sulfate, sodium potassium sulfate, strontium acetate, rubidium sulfate, rubidium benzoate, trisodium phosphate, sodium hydrogen phosphate and sodium bicarbonate.

Solubility will to some extent set anupper limit on salt concentration in the electrolyte solution, although if considered on the basis of water solubility in the salt, fairly low concentrations of water can be employed, but in general there will be at least 5% or so by weight of water or other proton donor present to avoid excessive production of higher polymeric materials, and water will gener- 4 ally constitutemore than 15 or 20% by weight of the or any electrode which is inert under the reaction conditions, is immersed in an anolyte contained in the porous cup. The anolyte is an aqueous solution of the salt. When there is employed no diaphragm in the cell, stirring can be employed for 'pH control. Thereby the anode is subjected to little or no attack; so that the anode, can be of substantially any electrode material. An anode comprising lead deposited on a copper screen can thus be employed. The cathode, which may be mercury, lead or another metal, and the porous cup, if one is employed, are submerged in the solution of alpha,beta-olefinic carboxamide in the concentrated aqueous salt or a mixture of the same with a polar solvent. The entire cell may be cooled by a jacket containing a coolant, and both the anode and cathode chambers m'ayflbe equipped with condenser's. However, as will be hereinafter shown, the increase of temperature which is produced during electrolysis generally does not result in so much of a decrease in yield that cooling other than with circulating water is economically required. Generally, the electrolysis can, for example, be conducted at a temperatureof from, say, less than about 10 C., and up to almost the refluxing temperature of the electrolytic bath and at higher temperatures, under pressure. Actually, slightly higher than ordinary ambient temperatures are conducive to improved yields, higher amide solubilities and lowered electrical resistance. This is to some. extent counterbalanced by the tendency of some diaphragm material such as cationic membrances to deteriorate at elevated temperatures, say of C., or the like and the tendency of some amides to vaporize at higher temperatures. It is generally advantageous to operate in the range of about 40 to about 60 C. Stirring of the solution during the electrolyses, if desired, may be conducted by mechanical or magnetic means. During the electrolysis, the pH ofthe catholyte may be controlled as hereinbcfore described. The quantity of current which is supplied to the cell will vary with the nature and quantity of the bath and of the electrodes and with the operating temperature, but will ordinarily be at a rate greater than 0.5 ampere and in the order of a current density of, say, from 2.0 to 20.0 or 40 or more amperes/dm. (dm. refers to the area in square decimeters of cathode surface). The etficiency of the process is, to some extent, dependent on the current density used. Thus for the efficient production of adipamide the current density should be at least about 5 arnperes/dm. and practical production rates ordinarily require the use of much higher current densities.

It is important to note that the present process involves an actual electrochemical reduction in which an electric potential is actually applied to a solution of the olefinic compound and current passed therethrough while the solution is in contact with the cathode, thereby involving a radical departure from such indirect methods as preparing sodium amalgam by electrochemical reduction of sodium salts, followed by mere contacting of a solution of the olefin with the sodium amalgam.

After the electrolysis, the hydrodimerization product maybe separated from the reaction mixture by isolating procedures known to those skilled in the art, e.g., by extraction, fractionation, etc. Generally, the reaction mixture is neutralized and the organic phase is separated by decanting and/or solvent extraction. After removing any residual inorganic matter by washing with water, the organic material is distilled to remove solvent and to give as residue the hydrodimerization productand any uncoverted olefinic monomer, together with by-products, if any. These may be separated from each other, e.g., by fractional distillation, etc. In experimental runs, results of the electrolysis can be conveniently arrived at, when the-products are liquid, simply by analytical determination of the hydrodimerization product and of the unconsumed monomer, if any, e.g., by vapor phase chromatography.

The following equations are illustrative of the proposed The proposed mechanism is in sharp contrast to the free radical mechanism which presumably prevails in strongly acid media to produce polymeric products from acrylic monomers.

(V) V acrylonitrile polyacrylonitrl'le and in a related process pinacols from ketones. It will be noted that the proposed mechanism to adipamide avoids the free radical of type V, as would appear essential for any mechanism to have validity in view of the known propensity of acrylamides to polymerize in the presence of free radicals. The proposed addition of two electrons to one molecule and its coupling with a molecule to which no electrons have been added is also supported by results described in my copending application S.N. 163,028 filed December 29, 1961, which relates to coupling of two different olefinic compounds at cathodic potentials suflicient to supply electrons to only one of the olefinic compounds.

The proposed mechanism to adipamide also explains the significance of the acrylamide concentration. For if the ion II encounters a high concentration of water molecules, rather than acrylamide molecules, it will take up two hydrogen ions from the water to form propionamide; thus it is necessary to maintain a high acrylamide concentration to avoid this simple reduction. Similarly, hydrogen ions present under acidic conditions enter into an interfering reaction with ion II by adding to II form propionamide. While water molecules can interfere, some water or other source of proton donor is necessary to provide hydrogen to convert III to adipamide and avoid a tendency toward polymerization. Thus the catholyte will ordinarily comprise by weight or more water, although even a few percentage points of water is ordinarily sutficient.

Of course, a certain minimum of water is advantageous in lowering electrical resistance.

The applicant does not intend to be limited to any particular mechanism, as the demonstrated results are obtained regardless of the mechanism advanced in explanation thereof. The proposed mechanism will aid in understanding the process, however, and in explaining the significance of certain departures from the prior art and of certain requirements for the process.

It is desirable to avoid acidity in order to effect the process of the present invention, both because of interfering polymerization reactions which occur in acidic media,

and because of the discharge of hydrogen ions which occurs circa --1.5 volts. If only a small .amount of hydrogen ions are present at the start of electrolysis, itmay be simple to electrolytically discharge such ions at ode until the pH goes over 7 and then to proceed with the hydrodimerization while maintainingalkaline conditions.

The invention is further illustrated by, but not limited to, the following examples.

Example 1 During a period of 3 hours an electric current was passed through a cell containing ml. of mercury as cathode and a platinum anode in a porous porcelain cup 1 containing as anolyte 20 ml. of a 75% aqueous solution of tetraethylammonium p-toluenesulfonate and 20 ml. of water, said cup being completely immersed in a catholyte consisting of 104 g. of said 75% aqueous-sulfonate solution, 104 g. of the N,N-diethyl.acrylamide and 52 g. of water. The concentrated solution of said amide in the catholyte was maintained at from 24-30" C., and the pH of'the catholyte was maintained just alkaline to phenol red by addition of 2.75 ml. acetic acid at intervals. The operation was conducted for a total of about 8.7 amp.-hrs., a cell voltage of 37-275 volts and a cathode voltage as determined against the saturated calomel electrode of from 1.88 to -l.95. When the current was discontinued, the catholyte was neutralized with acetic acid, extracted with six 50 ml. portions of methylene dichloride, washed and dried over potassium carbonate. The dried extracts were then concentrated on a water bath to remove the methylene dichloride and the residue was distilled to remove material boiling below 72 C./ 3.7 mm. Subsequent distillation of the residue through micro apparatus gave the fraction B.P. 182 C./2.2 mire-188 C./1.6 mm., which crystallized upon cooling. Trituration and washing with hexane gave the substantially pure N,N,N,N'- tetraethyl adipamide, M.P. SO-51 C.. which analyzed 65.47% car bon, 10.60% hydrogen and 11.13% nitrogen as against 65.59%, 11.00% and 10.93%, the respective calculated values. The yield of tetraethyl adipamide was 73% (crude product based on current employed).

Example 2 This example shows hydrodimerization of N,N-diethylcrotonamide.

During a period of about 3 hours, an electric current was passed'through a cell containing ml. of mercury as cathode and a platinum anode in a porous porcelain cup containing 20 ml. of 75% aqueous solution of tetraethylammonium p-toluenesulfonate plus 20 ml. of water, said cup being completely immersed in a catholyte consisting of 104 g. of a 75% aqueous solution of tetraethylammonium-p-toluenesulfonate, 104 g. of N,N-diethyl crotonamide and 52 g. of water. The operation was conducted at a temperature of from 25-30 C., a cell voltage of 29.2 to 36.5 volts, and a cathode voltage as determined against the saturated calomel electrode of from -1.92 to --2.12 for about 8.6 amp-hrs. During the electrolysis the pH of the catholyte was maintained just alkaline to phenol red by addition of 2.50 ml. of glacial acetic acid.

When the current was discontinued, the catholyte was neutralized with acetic acid, extracted with ether six times, and the ether extracts washed with water and dried over potassium carbonate. Ether was removed from the dried product to give 87.4 g. of residual liquid which was vacuum distilled to remove material boiling below 88% C./5 mm. to obtain as residue crude N,N,N',N'-tetraethyl-3,4- dimethyladipamide. The crude product was vacuum-distilled; the pure product boiled at 166/0.36 mm. or 171/0.40 mm., n 1.4754. Analysis gave 67.46% carbon, 11.55% hydrogen, 9.92% nitrogen, mol. wt. 281 as against calculated values of 67.56, 11.03, 9.85 and 284.4, respectively. The yield was 53%, based on current employed.

the cath- Example 3 An 85 gram amount of acrylamide containing a trace about three hours. The cell temperature was about 40 C., during the electrolysis and the cathode potential l.95

volts. About 3 ml. acetic acid was added durin'gthe electrolysis to prevent excess alkalinity. The cell contentsv were cooled to room temperature, separated. from the mercury, diluted with water andfiltered. The deposit on the filter was washed with water and oven-dried to 7.1 grams. The melting point of the pure white adipamide product was 228-229 C., compared to 228-229 C., for a mixed melting point with a known adipamide sample, M.P. 229-230 C. Evaporation of the filtrate and washings left some polyacrylamide residue. It should be noted that by the foregoing procedure an alpha,beta-olefinic amide is hydrodimerized directly by an electrolytic procedure, although such amides containing free hydrogen on the amide nitrogen are not successfully hydrodimerized by such indirect electrolytic procedures as reduction with sodium amalgam. I

Example 4 A 57.7 gram amount of the diethylamide of cinnamic acid was dissolved in a catholyte prepared from 101.2 grams of an 80% by weight concentration of tetraethylammonium p-toluenesulfonate in water and 86.6 grams dimethylformamide. A 110 ml. amount of mercury was provided as cathode, and a solution of the same ammonium salt in a porcelain cup was used as anolyte with a platinum anode. Current of 23 amperes was employed for a total energy input of about 3 ampere-hours. The cell temperature during the electrolysis was about 35 C., and the cathode potential about -1.7 volts. The reaction solution was removed from the cell, diluted with water, extracted several times with methylene dichloride and the extracts were dried over Drierite. The methylene chloride was removed by evacuation over a water bath and the residue was dissolved in absolute alcohol which was then removed by warming and evacuation. Trituration of the residual syrup with ether caused crystallization. The crystals were filtered and washed several times with dry ether, and the ether was removed from the filtrate to leave a syrup. The syrup was dissolved in hot absolute alcohol and water was added to cause an oil to separate. The solvents were removed by warming with evacuation, and the residual oil was taken up in benzene and passed through an A1 column, and the eluant triturated with petroleum ether and filtered; another fraction was obtained by eluting the column with ethanol and evaporating the ethanol, and both fractions were then recrystallized from water and dried. The N,N,N',N' -tetraethyl-3,4-diphenyladipamide, M.P. 47- 48 C., analyzed as follows-Calcd: C, 76.43; H, 8.88; N, 6.85; molecular weight, 408.6. Found: C, 76.12; H, 8.95; N, 6.70; molecular weight, 389.

Various other types of salts can be substituted for the ammonium sulfonate salts in the foregoing procedures. For example, methyltributylammonium methosulfate or other alkyl sulfates are suitable. Similarly methyltri-nbutylphosphonium p-toluenesulfonate or other phosphonium salts can be employed, particularly in view of the reported 2.2 to 2.3 volt (vs. standard calomel elec' trode) discharge potential of phosphonium ions.

When the procedure of the foregoing examples is followed, but employing only about by weight tetraethylammonium p-toluenesulfonate and as much of the A current of about 3 1 amperes was passed through the cell at about 22 volts for olefinic' carboxamide, for example that of Example 1, as will dissolve fairly substantial yields of the corresponding hydrodimer are obtained, although markedly inferior to those obtained at higher carboxamidc concentrations. However; when the tetraethylammonium ,p-tolucnesulfo nate concentration is 1%, the yields utilizing comparable olefinic carboxamide concentrations are much lower and of little practical significance. For this reason the concentration of the salt catholyte is important to the results attained.

Example 5 Following the general procedure of Example 1 but employinga 5% by weight solution of NaCl as catholyte and slightly over 5% by weight N,N-diethyl acrylamide, a very small amount of tetraethyl adipamide can be obtained.

Example 6 By substituting strontium chloride for the sodium chloride in Example 5, a similarly small amount of tetraethyladipamide can be obtained.

The above examples and data are illustrative of the hydrodimerization of alpha,beta-'olefinic amides. Specific process conditions may vary, of course, with different cell structures, with ratio of volume of catholyte to surface area of cathode as well as with other variables such as temperature, cathode voltage, current density, etc. Moreover, a number of cells can be combined into a single -unit, and the process can be carried out continuously by means of a circulating pump whereby the catholyte is withdrawn from the cell during the process, the

hydrodimerization product is separated therefrom, and

the residue is reintroduced into the cell together with additional olefinic compound to make up the initial strength.

The presently provided process provides a very simple and economical method for the manufacture of a great many aliphatic polyfunctional compounds, particularly the di-and tetra-carboxamides. The electrolytic process of this invention is advantageous in that, during the electrolysis, electrolyte is not consumed, only a minor proportion, if any, of the olefinic amide monomer is converted to the saturated monomer, and the electrolysis can be conducted if desired without the use of cost-increasing cooling systems and with highly efficient utilization of electric current. i

The process of this invention is particularly useful in those instances in which the dior tetra-functional alkanes have been obtainable only with difficulty or not at all by other processes. By hydrodimerizing an olefinic amide, it often is possible to obtain, using the process of this invention, a branched paraffinic amide more easily and more economically than otherwise would be possible. For example, the alpha-alkylacrylamides are hydrodimerized to the 2,5-di-alkyladipamides. The positioning of the two alkyl groups in this instance is of interest because superior resinous products of the polyamide'type are obtainable by reaction of dicarboxylic compounds with 2,5-dimethylhexamethylenediamine. The parafiinic and other diamides prepared by the present process are generally useful in the manufacture of high-molecular weight condensation polymers, e..g., by reaction with dihydroxy or dicarboxylic compoundstand the tetrafunctional compounds, as well as the difunctional compounds, are efiicient plasticizers for synthetic resins and plastics.

It is obvious that many variations may be made in the process of this invention without departing from the spirit and scope thereof.

What is claimed is:

1. A method of producing hydrodimers of alpha,betaolefinic carboxamides which comprises subjecting a solution of the carboxamides to electrolysis by passing an electric current through said solution in a divided cell in contact with a cathode under substantially non-polymerizing conditions, causing development of the cathode potential required for hydrodimerization of the carboxamide, the solution comprising water, more than about by weight of the carboxamide and to make the solution by weight of the carboxamide and to make the solution conductive at least 5% by weight of a supporting elec trolyte salt which provides a cation discharging at cathode potentials more negative than that at which hydrodimerization of the carboxamide occurs and more negative than that at which sodium discharges, and recovering in substantial yield hydrodimer having twice the carbon atoms of the starting carboxamide, the said electrolysis being conducted in a cell in which both cathode and anode are in actual physical contact with electrolyte.

2. A method of producing hydrodimers of aliphatic alpha,beta-olefinic carboxamides in substantial yield which comprises subjecting a solution of aliphatic alpha, beta-olefinic carboxamide to electrolysis by passing an electric current through said solution in contact with a cathode, causing development of the cathode potential required for hydrodimerization of the carboxamide, the solution consisting essentially of water, more than about 5% by weight of the carboxamide, and at least 5% by weight of supporting electrolyte salt to make the solution conductive, and recovering in substantial yield hydrodimer in which coupling has occurred between corresponding carbon atoms of two molecules of the starting carboxamide, the said carbon atoms being in the beta-position of the olefinic bond with respect to a carboXamide group of the starting carboxamide, the said hydrodimer having twice the carbon atoms of the starting carboxamide, the said electrolysis being conducted in a cell in which both cathode and anode are in actual physical contact with electrolyte.

3. The method of claim 2 in which the electrolysis is carried to more than 50% conversion to the hydrodimer.

4. The method of claim 2 in which a divided cell is employed and in which the average carboxamide concentration is greater than 15% by weight of the catholyte.

5. The method of claim 2 in which the pH in the bulk of the solution is in the range of about 6 to about 12.

6. The method of claim 2 in which the salt provides a cation discharging at substantially more negative cathode potentials than that at which the hydrodimerization of the carboxamide occurs.

7. The method of claim 2 in which a divided cell is. employed and the catholyte is prevented from becoming excessively alkaline by providing acid thereto to counteract the alkalinity developed by discharge of ions at the cathode.

8. The method of claim 1 in which the salt concentration constitutes more than by weight of the salt and water present in said solution.

9. The method of claim 2 in which the cathode is lead.

10. The method of claim 2 in which the olefinic compound is an N,N-dialkylacrylamide and the pH of the catholyte is maintained between 7 and 9.5.

11. The method of claim 2'in which the electrolyte comprises a salt selected from the group consisting of amine and ammonium sulfonates and alkylsulfates.

12. The method of claim 2 in which a polymerization inhibitor is employed.

13. The method of claim 1 in which the pH in the bulk of the solution is in the range of about 6 to 12.

14. The process of claim 2, further limited in that the olefinic compound is an alk-l-enyl carboxamide of from 3 to 8 carbon atoms.

15. The process of claim 2, further limited in that the olefinic compound is an N,N-dialkylamide of an alpha,beta-mon-olefinic carboxylic acid having from 1 to 5 carbon atoms in each alkyl radical and from 3 to 8 carbon atoms in the acid portion of the molecule.

16. A process for conducting the hydrodimerization of an alk-l-enyl carboxamide of from 3 to 8 carbon atoms, which comprises subjecting to electrolysis, in contact with a cathode having a hydrogen overvoltage greater than that of copper, a solution comprising water, the carboxamide, and a saturated tetraalkyl ammonium salt of an alkaryl sulfonic acid wherein the total number of carbon atoms in the sulfonic acid is from 7 to 12 and the total number of carbon atoms in the salt-forming radical is from 4 to 20, the concentration of the carboxamide in the solution being from about 10% to 50% by weight of the solution, the concentration of said salt in the solution being above about 30% by weight of the total amount of water and salt present in said solution and up to saturation.

17. The process of claim 2 in which the carboxamide is a beta-phenylacrylamide.

18. The process of claim 2 in which the carboxamide is acrylamide.

19. The process of claim 2 in which the carboxamide is a N,N-dialkylcrotonamide in which the alkyl groups contain up to 5 carbon atoms.

20. The method of claim 2 in which a polar solvent is employed along with water.

.21. A method of producing hydrodimers in better than 50% yield which comprises subjecting a solution of an alpha,betaolefinic carboxamide to electrolysis by passing an electric current through said solution in contact with a cathode having an overvoltage greater than that of copper under substantially non-polymerizing conditions, the current density being greater than 10 amperes/square decimeter of cathode surface, causing development of the cathode potential required for hydrodimerization of the carboxamide, the solution comprising water, more than 10% by weight of the carboxamide and supporting electrolyte salt to make the solution conductive, the amount of salt being above about 30% by weight of the total amount of salt and water present in said solution, the salt providing a cation discharging at cathode potentials more negative than that at which the hydrodimerization of the carboxamide occurs, and more negative than that at which sodium discharges, and obtaining hydrodimer in better than 50% yield.

22. The method of claim 21 in which the pH in the bulk of the solution is above 7 but below about 9.5.

23. The method of claim 21 in which a divided cell is employed so that the solution of olefinic compound does not contact the anode.

24. The method of claim 21 in which a tetraalkylammonium alkyl sulfate salt is used as electrolyte.

25. The method of claim 21 in which a tetraalkylammonium aromatic sulfonate salt is used as electrolyte.

26. A process for conducting the hydrodimerization of an aliphatic olefinic compound which is an N,N-dialkylamide of an alpha,beta-mono-olefinic carboxylic acid having from 1 to 5 carbon atoms in each alkyl radical and from 3 to 8 carbon atoms in the acid portion of the molecule, which comprises subjecting to electrolysis, in contact with a cathode having a hydrogen overvoltage greater than that of copper, a solution comprising water, the olefinic compound, and a salt selected from the class consisting of the saturated aliphatic and heterocyclic amine salts and the saturated aliphatic and heterocyclic quaternary ammonium salts of a sulfonic acid selected from the class consisting of aryl and alkaryl sulfonic acids wherein the total number of carbon atoms in the sulfonic acid is from 6 to 12 and the total number of carbon atoms in each of said amine and ammonium salt-forming radicals is from 4 to 20, the concentration of the olefinic compound in the solution being from about 10% to 50% by weight of the solution, the concentration of said salt in the solution being above about 30% by weight of the total amount of water and salt present in said solution and up to saturation, the pH of the solution being above 7, and the said electrolysis being conducted in a cell in 19 20, 7 which both cathode and anode are in actual physical FOREIGN PATENTS contact with electrolyte. 566,274 11/58 Canada References Cited by the Examiner UNITED STATES PATENTS 7 2,632,729 3/53 Woodman 204-72 2,726,204 12/55 Park ct al. -..'204-72 JOHN H. MACK, Primary Examiner. 5 WINSTON A. DOUGLAS, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,193,487 July 6, 1965 Harold Beuther et al It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Columns 5 and 6, Table V, first column, line 10 thereof,

for "C and C in/gas" read C and C in gas columns 7 and 8, Table VI, under the heading "Column 3 Table V", left-hand portion, line 3 thereof, for "11.5" read 11.6 same table, under the heading "Column 4 Table V", righthand portion, line 6 thereof, for "(1)" read (2) column 7, line 59, for "to" read of Signed and sealed this 21st day ofDecember 1965.

(SEAL) Attest:

ERNEST W. SWIDER Y EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A METHOD OF PRODUCING HYDRODIMERS OF ALPHA, BETAOLEFINIC CARBOXAMIDES WHICH COMPRISES SUBJECTING A SOLUTION OF THE CARBOXAMIDES TO ELECTROLYSIS BY PASSING AN ELECTRIC CURRENT THROUGH SAID SOLUTION IN A DIVIDED CELL IN CONTACT WITH A CATHODE UNDER SUBSTANTIALLY NON-POLYMERIZING KCONDITIONS, CAUSING DEVELOPMENT OF THE CATHODE POTENTIAL REQUIRED FOR HYDRODIMERIZATION OF THE CARBOXAMIDE, THE SOLUTION COMPRISING WATER, MORE THAN ABOUT 5% BY WEIGHT OF THE CARBONAMIDE AND TO MAKE THE SOLUTION CONDUCTIVE AT LEAST 5% BY WEIGHT OF A SUPPORTING ELECTROLYTE SALT WHICH PROVIDES A CATION DISCHARGING AT CATHODE POTENTIALS MORE NEGATIVE THAN THAT AT WHICH HYDRODIMERIZATION OF THE CARBOXAMIDE OCCURS AND MORE NEGATIVE THAN THAT AT WHICH SODIUM DISCHARGES, AND RECOVERING IN SUBSTANTIAL YIELD HYDRODIMER HAVING TWICE THE CARBON ATOMS OF THE STARTINT CARBOXAMIDE, THE SAID ELECTROLYSIS BEING CONDUCTED IN A CELL IN WHICH BOTH CATHODE AND ANODE ARE IN ACTUAL PHYSICAL CONTACT WITH ELECTROLYTE. 